1) Field of the Invention
The present invention relates to a vacuum pump and a vacuum apparatus equipped with the vacuum pump.
2) Description of the Related Art
In a case where dry etching, CVD, spattering, ion injection, etc. are performed in a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, etc., a vacuum pump such as a turbo molecular pump is widely used to perform vacuum processing by discharging the processing gas within a chamber.
FIG. 8 shows a typical turbo molecular pump which has been used.
As shown in FIG. 8, the turbo molecular pump has stator vanes and rotor vanes which are respectively disposed on a stator portion and a rotor portion in multiple stages in an axial direction, so that by rotating the rotor portion at a high speed with a motor an exhaust (vacuum) action occurs from an intake port side, i.e. the upper side in the drawing, to an exhaust port side, i.e. the left and lower side of the drawing.
FIG. 9 shows a typical vacuum apparatus in which the turbo molecular pump of this type is mounted to a chamber.
As illustrated, the vacuum apparatus has a stage 12 which is located within a chamber (container) 10 so that a sample 11 or the like can be placed on the stage 12, and a drive mechanism 13 which is located below the stage 12 and outside the chamber 10 so as to rotate the stage 12 or perform other functions. A turbo molecular pump 15 is mounted from the outside of the chamber 10 onto an exhaust port 14 portion located at the lower surface (or side surface) of the chamber so as to discharge the gas existing within the chamber 10.
However, if the sample 11 occupies a certain degree of area, the pressure in a side A closer to the turbo molecular pump 15 is lower, whereas the pressure in a side B farther therefrom is higher since the turbo molecular pump 15 is situated away from a center of the sample 11. That is, non-uniform pressure distribution is created in the vicinity of the sample 11.
Such non-uniform pressure distribution within the chamber 10 results in non-uniformity in various conditions such as a manufacturing condition, a reaction condition, a measurement condition for the sample 11. In particular, in case of the semiconductor manufacturing process, since a wafer disposed as the sample 11 on the stage 12 has been increasing in diameter recently, a pressure difference is likely to be caused around the wafer, which hinders the manufacturing of the uniform products.
In an attempt to make the pressure within the chamber 10 uniform, vacuum apparatuses of the following arrangements have been proposed.
For example, as shown in FIG. 10, a plurality of exhaust ports 14 are provided (four holes are provided in the drawing) within the chamber 10 at equidistance around the stage, and the exhaust ports 14 are connected through a branch pipe 17 to a single turbo molecular pump 15. In addition, the stage is disposed at a central position with respect to the exhaust ports 14 and the stage drive mechanism is disposed at the central portion circumscribed by the branch pipe 17 although they are not illustrated in FIG. 10 for convenience in explaining the arrangement of the piping.
By locating the exhaust ports 14 at equidistance around the sample 11 in this manner, it is possible to make the pressure around the sample 11 uniform.
As shown in FIG. 11, such a vacuum apparatus is also available that a plurality of exhaust ports 14 are provided (four holes are provided in the drawing) within the chamber 10 at equidistance around the stage, and the exhaust ports 14 are connected to respective turbo molecular pumps 15.
The vacuum apparatus thus constructed can eliminate the non-uniformity of the pressure distribution since the exhaust action is carried out by the turbo molecular pumps 15 using the plurality of exhaust ports 14 that are disposed uniformly around the sample 11.
Further, as shown in FIG. 12, such a vacuum apparatus is also available that a conductance adjustment plate 18 is disposed between the stage 12 and the exhaust port 14 within the chamber 10.
Only one exhaust port 14 is provided in this vacuum apparatus, but since the conductance adjustment plate 18 serves as a resisting plate against the exhaust or discharge flow, it is possible to suppress the non-uniformity in pressure distribution within the chamber 10.
The vacuum apparatus shown in FIG. 10, however, requires the turbo molecular pump 15 to be disposed at such a position as to avoid the interference with the drive mechanism that is located in the chamber 10. Accordingly, the branch pipe 17 is also required to be led to the turbo molecular pump 15 while avoiding the interference with the drive mechanism. This restriction in piping design is likely to cause the non-uniform conductance (exhaust resistance) of the pipe, and thus it is required to additionally install a pressure adjusting valve at a location midway of the pipe or to partially modify the length or diameter of the pipe, which results in an increase in cost.
Further, the turbo molecular pump 15 of a larger exhaust speed is required due to the conductance of the branch pipe 17, and the entire cost for the apparatus is increased accordingly.
Moreover, although the vacuum apparatus shown in FIG. 10 is advantageous over the vacuum apparatus shown in FIG. 9 from the viewpoint of the uniform pressure distribution, the provision of only four exhaust ports 14 cannot solve such a pressure non-uniformity problem that a pressure difference is caused between the vicinity of each exhaust port 14 and the intermediate position between an adjacent exhaust ports 14 and 14. The provision of the increased number of exhaust ports 14 and the pipes may solve this non-uniformity problem, but such will further increase the cost.
In the case of the vacuum apparatus shown in FIG. 11, since an independent turbo molecular pump 15 is installed for a respective exhaust port 14, the apparatus is free from the increase of conductance due to the use of the branch pipe, but suffers from a problem in that the provision of the plurality of turbo molecular pumps results in the higher cost in comparison to the provision of the branch pipe. Further, similarly to the vacuum apparatus shown in FIG. 10, the apparatus encounters the pressure non-uniformity problem in which a pressure difference is caused between the vicinity of each exhaust port 14 and the intermediate position between the adjacent exhaust ports 14 and 14.
In the case of the vacuum apparatus shown in FIG. 12, the provision of the conductance adjusting plate 18 increases the cost, and is insufficient to effectively eliminate the non-uniformity of the pressure distribution.
Accordingly, a primary object of the present invention is to provide a vacuum pump of a novel arrangement, which can eliminate the non-uniformity of the pressure distribution around the stage.
A secondary object of the present invention is to provide a vacuum apparatus of a novel arrangement, which can eliminate the non-uniformity of the pressure distribution around the stage.
According to a first aspect of the present invention, there is provided a vacuum pump which comprises: an outer casing including an inner cylinder having a hollow portion inside thereof, the hollow portion being communicated with an atmospheric air and capable of accommodating a device therein, an outer cylinder disposed outside the inner cylinder, and a bottom surface plate closing a gap between the outer cylinder and the inner cylinder at one end side; an exhaust port disposed at the one end side of the outer casing; a rotor main body disposed between the inner cylinder and the outer cylinder; a bearing supporting the rotor main body; a motor which rotates the rotor main body, the motor being disposed between the inner cylinder and the rotor main body or between the outer cylinder and the rotor main body; and a pump mechanism which carries gaseous molecule from an intake port disposed at the other end side of the outer casing and discharges the gaseous molecule from the exhaust port, the pump mechanism being disposed between the inner cylinder and the rotor main body or between the outer cylinder and the rotor main body, to thereby achieve the primary object.
According to a second aspect of the present invention, in a vacuum pump as set forth in the first aspect of the present invention, a non-contact sealing mechanism is disposed at least on one of the one end side and the other end side so that a reverse flow of the gaseous molecule to the side where the pump mechanism is not disposed, between the inner cylinder and the rotor main body or between the outer cylinder and the rotor main body, is prevented.
According to a third aspect of the present invention, there is provided a vacuum pump comprising: an outer casing including an inner cylinder having a hollow portion inside thereof, the hollow portion being communicated with an atmospheric air and capable of accommodating a device therein, an intermediate cylinder disposed outside the inner cylinder, an outer cylinder disposed outside the intermediate cylinder, and a bottom surface plate closing a gap between the inner cylinder and the intermediate cylinder and a gap between the intermediate cylinder and the outer cylinder at one end side; an exhaust port disposed at the one end side of the outer casing; a communication hole disposed at the one end side of the intermediate cylinder; a rotor main body including an inner rotor main body disposed between the inner cylinder and the intermediate cylinder, an outer rotor main body disposed between the intermediate cylinder and the outer cylinder, and a connection plate connecting the inner rotor main body and the outer rotor main body to each other at an upper side of the intermediate cylinder; a bearing supporting the rotor main body; a motor which rotates the rotor main body, the motor being disposed between the intermediate cylinder and the inner rotor main body or between the intermediate cylinder and the outer rotor main body; and a pump mechanism which carries gaseous molecule from an intake port disposed at the other end side of the outer casing and discharges the gaseous molecule from the exhaust port, the pump mechanism being disposed between the inner rotor main body and the inner cylinder or between the outer rotor main body and the outer cylinder, to thereby achieve the object.
According to a fourth aspect of the present invention, in a vacuum pump as set forth in any one of the first to third aspects of the present invention, the pump mechanism applies vector momentum to the gaseous molecule using a threaded groove mechanism, a blade disposed on the rotor main body, a disk disposed on the rotor main body or a combination thereof, to thereby discharge the gaseous molecule.
According to a fifth aspect of the present invention, in a vacuum pump as set forth in any one of the first to third aspects of the present invention, the pump mechanism includes a volume transferring type pump mechanism.
According to a sixth aspect of the present invention, in a vacuum pump as set forth in any one of the first to fifth aspects of the present invention, the bearing includes a magnetic bearing.
According to a seventh aspect of the present invention, there is provided a vacuum apparatus using a vacuum pump as set forth in any one of the first to sixth aspects, the vacuum apparatus comprising: a container having an annular exhaust port; a stage disposed inside the exhaust port within the container; a stage drive mechanism disposed outside the container; and the vacuum pump in which the drive mechanism is accommodated within the hollow portion, wherein the one end side is mounted to the container such that the exhaust port is communicated with the intake port, to thereby achieve the secondary object.